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Turns out, the Crucial drives' "power loss protection" doesn't actually preserve data "in-flight" at the moment of power loss. It just prevents data "at rest" f

by rosser 11y ago

Turns out, the Crucial drives' "power loss protection" doesn't actually preserve data "in-flight" at the moment of power loss. It just prevents data "at rest" from being corrupted. This appears to apply to all the consumer-grade Crucial drives. See [1], money quote: "In the MX100 review, I was still under the impression that there was full power-loss protection in the drive, but my impression was wrong. The client-level implementation only guarantees that data-at-rest is protected, meaning that any in-flight data will be lost, including the user data in the DRAM buffer. In other words the M500, M550 and MX100 do not have power-loss protection -- what they have is circuitry that protects against corruption of existing data in the case of a power-loss." [1] http://www.anandtech.com/show/8528/micron-m600-128gb-256gb-1tb-ssd-review-nda-placeholder http://www.anandtech.com/show/8528/micron-m600-128gb-256gb-1...

userbinator 11y ago
That is true of ordinary HDDs too. Until data is written to the flash or platter itself, it hasn't been actually written. People don't expect files they haven't saved to be written and magically come back later if the power goes out, but they do expect that their drives will power back up with all the data that was last written intact.
- rosser 11y ago
  Yes, that's true. However, Crucial explicitly marketed their SSDs as having, quote, "power loss protection", pointing out the array of capacitors on the drive's PCB, and strongly implying that this feature included in-flight writes surviving a power loss (i.e., that the caps had enough capacity to enable flushing the DRAM buffer to the NAND media, much like the non Sandforce-based Intel SSDs — e.g., the 320 series from a few years back, or the current DC-3500 and -3700 drives). That, it turns out, isn't true. And that's a problem, because I and many others bought these drives on the basis of Crucial's implying they were power-loss durable. When enough people started reporting to Crucial support that their drives didn't, in point of actual fact, offer this feature, their marketing literature changed so as not to imply they did, and forum posts and reviews, like my previously-linked Anand Tech article, started pointing out that they didn't.

by rosser 11y ago

userbinator 11y ago

That is true of ordinary HDDs too. Until data is written to the flash or platter itself, it hasn't been actually written. People don't expect files they haven't saved to be written and magically come back later if the power goes out, but they do expect that their drives will power back up with all the data that was last written intact.

rosser 11y ago
Yes, that's true. However, Crucial explicitly marketed their SSDs as having, quote, "power loss protection", pointing out the array of capacitors on the drive's PCB, and strongly implying that this feature included in-flight writes surviving a power loss (i.e., that the caps had enough capacity to enable flushing the DRAM buffer to the NAND media, much like the non Sandforce-based Intel SSDs — e.g., the 320 series from a few years back, or the current DC-3500 and -3700 drives). That, it turns out, isn't true. And that's a problem, because I and many others bought these drives on the basis of Crucial's implying they were power-loss durable. When enough people started reporting to Crucial support that their drives didn't, in point of actual fact, offer this feature, their marketing literature changed so as not to imply they did, and forum posts and reviews, like my previously-linked Anand Tech article, started pointing out that they didn't.